A. Field of the Invention
This invention relates to the field of art of matrix switching networks.
B. Prior Art
In about the last 10 years, analog-hybrid simulation systems have improved considerably but there has not been a corresponding improvement in automating the process of programming analog-hydrid computers. Accordingly, analog-hybrid computers have still required their analog components to be patched together by hand in a patch board. There has been prior work directed toward the development of practical hardware for automatic patching as described in Hannauer, G.: "Automatic Patching for Analog and Hybrid Computers", Simulation, May 1969; Starr., D. and Jonsson, J. J.: "Design for an Automatic Patching System", Simulation, June 1968; Hannauer, G.: IEEE Transactions on Computers, December 1968; Gracon, T. and STrauss, J.: "A Decision Procedure for Selection Among Proposed Automatic Analog Computer Patching Systems", Simulation, September 1969; Howe, R. M., Moran, R. and Berge, T.: "Time-Sharing of Hybrid Computers Using Electronic Patching", Simulation, September 1970; and, Shoup, J. F. and Adams, W. S.: "A Practical Automatic Patching System for a Time-Shared Hybrid Computer", Simulation, April 1972.
In addition, the following laid open Japanese patent applications have also investigated this problem: lay-open No. 15057/1972, "Automatic Connector for Analog Computers"; lay open No. 16052/1972, "Interconnecting System for a Hybrid Computer"; lay-open No. 18244/1972, "Automatic Connection Type Analog/Hybrid Computer"; lay-open No. 77736/1973, "Hybrid Computer"; lay-open No. 78852/1973, "Hybrid Computer"; and, lay-open No. 79651/1974, "Central Exchange Automatic Connection System for Analog Computers".
Much of this prior art has been patterned after the three stage interconnecting network or switching matrix of Clos, C.: "A Study of Non-blocking Switching Networks", Bell System Tech. J., Vol. 32, pp. 406-424, 1953 and Duguid, A. M.: "Structural Properties of Switching Networks", Brown University, Progress Report BTL-7, 1959.
Generally, in these three stage interconnecting networks, it has been known that as connections are being made between input and output, at a certain point a switch block in a stage may not be able to make a certain connection. This is defined as a "block". In designing a switching matrix it has been known to attempt to provide a minimum number of switch blocks in order to have a nonblocking condition. For example, the above cited Clos article describes the design of such a network assuming nonblocking with a minimum number of switches based upon one input being connected to only one output. However in analog-hybrid applications, this one-to-one relationship is not necessarily used and there are other factors involved.
Specifically, in such analog-hydrid computers, connections may be rearranged or rerouted during programming if a blocked condition is found in a given path of interconnection. Thus a flexibility in manipulating connections is important since, for example, it may be desirable in a program to connect one input to any one or more of differing sets of integrators. While one method of rearrangeability is described in the cited Duguid article, both the Duguid and Clos systems assume as in telephone switching that each output is connected to exactly one input. However, in analog patching an analog-hybrid computer, it is frequently required that a particular component feed many other components. As for example, an output of a component may be a variable to be used as an input to several equations which defines "fan-out". Accordingly, the prior art has left much to be desired in an operable system which implements a minimum number of switching units for an optimal switching matrix to achieve both fan-out and rearrangeability or rerouting. Such a system while initially designed for analog-hybrid computer applications may have applications in other fields such as trunking long lines of analog signals generated by transducers.